We all love free apps, but it's hard to track when apps go on sale, and whether they're worth the trouble. Here's a trick for keeping track of on-sale apps, and making those sales last forever.

We've shared a few tools that help you track app sales, but they can be a pain. A lot of the apps that go on sale aren't very good, and while you can make a wish list, this doesn't help you discover new apps at all. Of course, we occasionally share cool apps in our Dealhacker posts, but what if you could get automatic email notifications for cheap, good apps whenever they went on sale? Here's a method—inspired by this Reddit post—to make that a reality.

The standard price tag on mobile apps isn't terribly high, but if your threshold is 99¢ you…
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Step One: Set Up App Deal Notifications with IFTTT

Previously mentionedIFTTT is an awesome webapp that lets you perform a certain action whenever the webapp detects something you tell it to monitor. Today, we're going to tell it to email us every time it detects an app deal we like. Here are a few example recipes you can use to achieve this:

Wouldn't it be handy if every time someone tagged a photo of you on Facebook, that pic were…
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Notifications for Lifehacker's Dealhacker Posts: Here at Lifehacker, we constantly monitor app deals so you don't have to wade through them all the time, sharing our favorite useful and productive apps whenever they have a significant drop in price. This recipe, which you can grab here, emails you every time we post a new Dealhacker post so you can stay on top of our favorite apps.

Notifications for iTunes' Free App of the Week: This recipe, which you can get here, sends you an email whenever the @AppStore Twitter account tweets with the #FreeAppoftheWeek, notifying you of that week's free app on iTunes..

Notifications for Amazon's Free App of the Day: Amazon's free app of the day isn't always as good as Apple's, but if you wan to keep track, this similar IFTTT recipe can help. It emails you each of @AmazonAppADay tweets its deal of the day.

Those are just a few examples—you can create as many as you want in IFTTT, and for whatever services or deals you want to follow. This system not only saves you money, but helps you notice apps you wouldn't have otherwise tried out. If you're going to do email notifications, though, I recommend you create a filter for emails from IFTTT so your inbox isn't flooded with notifications.

Once you have that set up, the rest is easy: When you see an app that's on sale for free, download it, even if you don't think you want it right now. Why? Because once you download an app, it's linked to your account, and you'll be able to download it for free forever—even if the app goes back to its regular price! Redditor TreyFexplains:

The free app this week is Kayak Pro. It's a travel app with a lot built in (baggage fee calculator, itinerary settings, terminal maps) and you can search for travel related deals. It's normally $.99 but this week it's free.

I know what you're thinking. "I'm not doing any traveling soon".

This is the beauty of iOS. Download the free app, and delete it. When you know you're going to travel, go into your recently purchased apps and re-download it. It will be free and won't take up space until you need to download it.

iOS: Kayak, one of our favorite travel apps for iOS and Android, is offering its Pro version for…
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You don't need to download every app you see, just the ones that you might want down the road—the ones that are popular, come highly recommended by your favorite tech blog (ahem), and so on. It's especially handy when you think an app has potential, but would be better with a couple extra features—if and when they improve the app, you'll be able to grab it for free. And if not, you've only wasted a couple seconds attaching it to your account. As long as you delete it, it won't even clutter up your phone.